<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>递归</title>
</head>
<body>
    
</body>
<script>
function sum(x) {
    if (x === 1) {
        return 1;
    }
    return x + sum(--x);
}

console.log( sum(10) );
console.log( sum(55555) );
</script>
</html>